Ultrasonic wave sealing method for container

ABSTRACT

An ultrasonic container sealing method of sealing a closure  12  to a container main body  11  with use of an ultrasonic horn  54  having a sealing action face  53  comprises applying pressure to a lap of an outer peripheral portion of the closure  12  and a flange  24  of the container main body  11  as lapped over each other by the sealing action face  53,  and causing ultrasonic rotational vibration in a rotating direction about an axis parallel to the direction of application of the pressure to act on the sealing action face  53.

TECHNICAL FIELD

[0001] The present invention relates to a method of ultrasonicallysealing containers with use of an ultrasonic sealing device for sealinga closure, spout plug or other container component to the main body ofthe container.

BACKGROUND ART

[0002] Such an ultrasonic sealing method for containers uses anultrasonic horn having a sealing action face for sealing a containercomponent to the main body of the container. The sealing action faceapplies pressure to the portions to be sealed of the container componentand the container main body as lapped over each other, and ultrasonicreciprocating vibrations in an axial direction parallel to the directionof application of the pressure are caused to act on the sealing actionface.

[0003] Also known are other sealing methods which use no ultrasonicsealing device, such as high-frequency induction sealing, high-frequencydielectric sealing and heat sealing with use of a heat plate.

[0004] The ultrasonic reciprocating vibrations applied to the horn acton the portions of the container to be sealed as if beating, aretherefore transmitted to the wall of the container or to a head spaceinside the container, and vibrate the contents of the container. Thisentails the likelihood that the contents will be broken, or the contentswill be forced out of the container during sealing by being shakenvigorously or becoming vaporized depending on the conditions involved,if the contents are liquid. To preclude these phenomena, the containerneeds to have an increased head space.

[0005] Furthermore, the conditions for producing satisfactory seals aregreatly limited; unless the conditions are fulfilled, a thin wallportion of component of the container will be broken, or pinholes arelikely to develop in the seal joint.

[0006] In the case where axial ultrasonic reciprocating vibrations arecaused to act on the sealing action face for sealing, the sealingoperation requires a great pressure. The sealing method is thereforeunsuited to containers which are low in buckling strength. In addition,the great pressure must to be received in the vicinity of the portionsto be sealed. For this reason, there arises a need to provide a pressurereceiving flange on an opening-defining edge portion of the containermain body, or an attempt is made to cover the edge portion with askirted caplike closure. However, when the pressure is to be received bythe flange, the skirt becomes an obstacle and can not be formed on thecap, hence limitations on the design of the container and the cap.

[0007] Since ultrasonic sealing can not be resorted to for sealingcontainers of small strength or skirted closures, high-frequencyinduction sealing or high-frequency dielectric sealing is used, whereasthe use of high-frequency sealing requires the use of aluminum or likematerial which induces high-frequency waves for the portions to besealed, or the high-frequency dielectric sealing necessitates a materialamenable to this method of sealing, hence limitations on the materialsfor the container or closure and problems to be involved in recyclingthe material.

[0008] The heat sealing operation requires time, is inefficient, and isinfeasible for containers and closures having a large thickness.

[0009] An object of the present invention is to overcome all the aboveproblems and to provide a method of ultrasonically sealing containerswhich will not adversely affect the contents of the container duringsealing and which can be practiced under widely varying conditions witha high efficiency.

DISCLOSURE OF THE INVENTION

[0010] In sealing a container component to a container main body usingan ultrasonic horn having a sealing action face, the present inventionprovides an ultrasonic container sealing method comprising applyingpressure to portions to be sealed of the container component and thecontainer main body as lapped over each other by the sealing action faceand causing ultrasonic rotational vibration in a rotating directionabout an axis parallel to the direction of application of the pressureto act on the sealing action face.

[0011] With the ultrasonic container sealing method of the invention,the ultrasonic rotational vibration to be caused to act on the sealingaction face does not act as if beating the wall of the container butacts in a direction along the container wall. Accordingly, the vibrationproduces no adverse effect on the contents during sealing. Furthermore,the pressure to be applied can be small. Moreover, advantages are alsoavailable such as a reduction in the wall thickness of containers,savings in resources and cost reductions. The materials for thecontainer body and container components are not limited. For thisreason, the container main body and closure can be produced fromaluminum-free materials, hence ease of recycling.

[0012] When ultrasonic vibration other than the ultrasonic rotationalvibration is caused to act on the sealing action face in combinationwith the rotational vibration, an efficient sealing operation can beperformed by utilizing the combined vibrations of ultrasonic waves.

[0013] If the sealing action face is provided with indentations andprojections in advance for improving the sealing conditions, the sealingoperation can be conducted under widely varying conditions.

[0014] The container main body may be provided around an edge portionthereof defining an opening with a flange forming the portion to besealed, and the container component may be in the form of a cap to befitted over the opening-defining edge portion of the container main bodyand having a skirt at an outer peripheral edge portion providing theportion to be sealed.

[0015] When the pressure to be applied by the ultrasonic horn isreceived by a bottom of the container main body, the container becomeseasy to handle for sealing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is an exploded perspective view of a container main bodyand a closure which are joined by the sealing method of the invention.

[0017]FIG. 2 is a diagram for illustrating how to seal a container by asealing device for practicing the method of the invention.

[0018]FIG. 3 is an enlarged view showing a sealing action face at theforward end of a horn of the sealing device.

[0019]FIG. 4 is an enlarge view corresponding to FIG. 3 and showinganother example of sealing action face of the device.

[0020]FIG. 5 is an enlarge view corresponding to FIG. 3 and showinganother example of sealing action face of the device.

[0021]FIG. 6 is a diagram for illustrating other mode of sealing acontainer.

[0022]FIG. 7 is a diagram for illustrating other mode of sealing acontainer.

[0023]FIG. 8 is a diagram for illustrating other mode of sealing acontainer.

[0024]FIG. 9 is a diagram for illustrating other mode of sealing acontainer.

BEST MODE OF CARRYING OUT THE INVENTION

[0025] Embodiments of the invention will be described below withreference to the drawings.

[0026]FIG. 1 shows a container comprising a main body 11 and a closure12. The container main body 11 and the closure 12 are molded from thesame kind of thermoplastic synthetic resin. Examples of usefulthermoplastic resins are PS, PP, PE, PET, PEN, etc. or a compositematerial of such resins.

[0027] The container main body 11 is in the form of a bottle and has atubular trunk 21 having a bottom. The trunk 21 has an opening 23 definedby an edge provided with a flange 24.

[0028] The closure 12, which is in the form of a cap of small height,comprises an annular fitting recessed portion 31 in the form of achannel and facing downward, a flat platelike web portion 32 integralwith the lower end of inner side wall of the recessed portion 31, askirt 33 extending downward from the outer side wall of the recessedportion 31, and a knob 34 integral with a part of lower end of outerperiphery of the skirt 33.

[0029] The fitting recessed portion 31 is fitted over the flange 24, andthe bottom wall of the recessed portion 31 is lapped over and sealedultrasonically to the top wall of the flange 24.

[0030]FIG. 2 shows a container holder 41, and an ultrasonic sealingdevice 42 disposed above the container holder 41 and facing verticallydownward.

[0031] The container holder 41 is supported by a compression coil spring43 on a horizontal lift plate 44. The sealing device 42 comprises adevice body 52 mounted on a support 51, and a horn 54 in the form of around rod, projecting downward from the device body 52 and provided atthe lower end thereof with a sealing action face 53 facing downward. Anunillustrated vibrating element is incorporated in the device body 52.The vibrating element causes ultrasonic rotational vibrations to act onthe sealing action face 53 of the horn 54 in a rotating direction aboutthe axis thereof as indicated by an arrow in FIG. 2.

[0032] The sealing action face 53 has a cavity 61 formed centrallythereof, and indentations and projections 62 formed around the cavity61. Examples of indentations and projections 62 are those provided byforming in the sealing action face 53 intersecting grooves 71 extendingin two directions as shown in FIG. 3, those provided by forming in thesealing action face 53 parallel grooves 72 extending in one direction asseen in FIG. 4, and those provided by forming in the sealing action face53 radial grooves 73 extending radially of the face as shown in FIG. 5.

[0033] Improved sealing conditions are available by providing suchindentations and projections 62. The sealing conditions are, forexample, the amplitude of ultrasonic waves, vibrating time, the pressureto be applied during sealing, the period of time during which thepressure is to be maintained, etc. These conditions can be set over wideranges.

[0034] When the spring 43 is compressed by raising the lift plate 44,with the bottom of the container main body 11 supported by the containerholder 41, the force of the spring causes the sealing action face 53 toapply pressure to the recessed portion 31 and the flange 24. When thevibrating element applies ultrasonic rotational vibrations to the horn54, the bottom wall of the recessed portion 31 is sealed to the top wallof the flange 24.

[0035] The pressing means may be one other than the spring. For example,a fluid pressure cylinder may be provided on the horn side.

[0036] Containers having shapes different from that of the one describedabove will be sealed in the modified modes to be described below.

[0037]FIG. 6 shows a container comprising a cuplike main body 81 and aclosure 82 in the form of a dome. The container main body 81 has aflange 83 around an edge portion defining an opening. The closure 82 hasa lower edge provided with a flange 84, which is lapped over the flange83 of the main body 81. The closure 82 is provided at its top with aspout (not shown), and a cap 85 is fitted over the spout.

[0038] The container main body 81 is fitted into a container holdinghole of a container holder 41 and has its flange 83 supported by an edgeportion of upper surface of a container holder 41 which portion definesthe container holding hole.

[0039] A sealing action face 53 has a cavity 61 which is so sized as toaccommodate the closure 82 nearly in its entirety. An inner edge portionof the face 53 defining the cavity 61 applies pressure to both theflanges 83, 84 of the container main body 81 and the closure 82, andultrasonic rotational vibrations are caused to act on the horn 54 inthis state.

[0040] In this case, the pressure for sealing is applied by pressingmeans provided on the ultrasonic sealing device 42, for example, by anunillustrated fluid pressure cylinder.

[0041]FIG. 7 shows a case wherein the lower surface of a flange 93 of aplug 92 having a cap is sealed to the outer surface of edge portion of aspout (not shown) which is provided on a top portion of the main body 91of a container having a gable top.

[0042] The container main body 91 is supported at its bottom by acontainer holder 41 which is fixedly supported.

[0043]FIG. 8 shows a case wherein a plug 102 is attached to a topportion of a container main body 101 having a gable top before the topportion is closed. The plug 102 is fitted into a spout 103 from insidethe container main body 101, with a flange 104 of the plug bearing onthe inner surface of an edge portion of the spout 103.

[0044] The flange 104 and the edge portion of the spout 103 are clampedbetween a horn 54 of an ultrasonic sealing device 42 and an anvil 111,and thereby subjected to pressure. Ultrasonic waves are produced in thisstate.

[0045] The ultrasonic sealing device 42 is provided with pressing meansfor applying pressure in this case as in the case shown in FIG. 6.

[0046]FIG. 9 shows a case wherein a plug 122 is sealed to a top portionof a bricklike container main body 121. The container main body 121 anda plug flange 123 are held between the horn 54 of a ultrasonic sealingdevice 42 and a container holder 41 from above and below.

[0047] In any of the above cases, ultrasonic rotational vibrations areapplied to the portions to be sealed. Already known as ultrasonicvibrations are ultrasonic reciprocating vertical vibrations parallel tothe axial direction of the horn, ultrasonic reciprocating horizontalvibrations orthogonal to the axial direction of the horn, and obliquevibrations comprising vertical vibrations and horizontal vibrations incombination. Depending on the material of the container on which thesealing conditions are dependent, it is effective to use combinedvibrations comprising ultrasonic rotational vibrations and otherultrasonic vibrations including the above ultrasonic vibrations.

INDUSTRIAL APPLICABILITY

[0048] The ultrasonic container sealing method of the invention issuitable for sealing, for example, a closure, plug or other containercomponent to a container main body with use of an ultrasonic sealingdevice.

1. In sealing a container component to a container main body using anultrasonic horn having a sealing action face, an ultrasonic containersealing method comprising applying pressure to portions to be sealed ofthe container component and the container main body as lapped over eachother by the sealing action face and causing ultrasonic rotationalvibration in a rotating direction about an axis parallel to thedirection of application of the pressure to act on the sealing actionface.
 2. An ultrasonic container sealing method according to claim 1wherein ultrasonic vibration other than the ultrasonic rotationalvibration is caused to act on the sealing action face in combinationwith the rotational vibration.
 3. An ultrasonic container sealing methodaccording to claim 1 or 2 wherein the sealing action face is providedwith indentations and projections in advance for improving the sealingconditions.
 4. An ultrasonic container sealing method according to anyone of claims 1 to 3 wherein the container main body is provided aroundan edge portion thereof defining an opening with a flange forming theportion to be sealed, and the container component is in the form of acap to be fitted over the opening-defining edge portion of the containermain body and having a skirt at an outer peripheral edge portionproviding the portion to be sealed.
 5. An ultrasonic container sealingmethod according to any one of claims 1 to 4 wherein the pressure to beapplied by the ultrasonic horn is received by a bottom of the containermain body.